An organic EL device is a device in which an emission layer is held between an anode and a cathode. Electrons and holes are injected from a cathode layer and an anode layer, respectively, and combined in the emission layer, thus causing the organic EL device to emit light.
When an organic EL device is used as a component of a display monitor, partial removal processing of its electrode layers and organic compound portion, which includes the emission layer, is indispensable and, as recent display apparatuses are acquiring higher definition, the removal processing is requested to improve in precision.
The partial removal processing of the electrode layers and the organic compound layer which constitute an organic EL device is accomplished specifically by a processing method that avoids mechanical contact, such as light irradiation. For example, Japanese Patent Application Laid-Open No. 2002-124380 discloses a method in which an organic compound layer on a glass substrate and on an ITO thin film is removed by laser ablation.
To give another example, Japanese Patent Application Laid-Open No. 2004-140003 discloses a method which uses laser ablation to perform microprocessing on a metal-based electrode layer placed on an organic compound layer.
A stacked type organic EL display apparatus laminates together two or more light-emitting devices each including an organic compound layer that is held between at least two electrode layers and that includes at least an emission layer. This type of organic EL display apparatus requires special processing to be performed on the electrode layers and the organic compound layers.
Specific examples of the special processing include forming openings at desired points in the respective organic compound layers in order to make a given organic compound layer emit light through pixel-basis electric connection with TFT circuits, which are formed on a substrate in advance. The examples also include removal processing for breaking up an electrode layer so that the electrode layer in one pixel is separated from the electrode layer in another pixel. The special processing leaves concavities in places where the openings are formed or part of the electrode layer is removed.
If an organic compound layer or an electrode layer is formed on the layer where those concavities were created, and then the processing method described in Japanese Patent Application Laid-Open No. 2002-124380 or Japanese Patent Application Laid-Open No. 2004-140003 is used to perform removal processing on the places having the concavities, the following problems may arise.
In the case of processing an organic compound layer, laser light incident upon the concavities is refracted and scattered unintendedly in the concavities and reaches unintended places.
This creates a change in the energy density distribution of laser light within an area where partial removal processing is performed, with the possible result that the processing rate is fluctuated to a degree that makes the processed shape deviate from design values.
For example, the change of the energy density distribution can cause the partial removal processing (formation of so-called contact holes) of a given organic compound layer to reach an electrode layer that is not to receive removal processing, thus bringing about unintended wire breakage.
In the case of removal processing of a given electrode layer, the change of the energy density distribution can cause the processing to reach an organic compound layer that is not to receive removal processing, thus exposing an electrode layer that underlies this organic compound layer.
As a result, if a different organic compound layer is laid on top thereof in the next step, the organic compound layer above the exposed electrode layer, which is not intended for light emission may emit light, depending on the electric potential of the underlying exposed electrode layer.
As described above, a stacked type organic EL display apparatuses thus have a problem of unintended removal processing which is brought about by a failure in accomplishing uniform removal processing of an organic compound layer or an electrode layer, and which results in a short circuit, or unintended light emission in a pixel when its adjacent pixel emits light.